Fine Tuning The VIC's Audio And Video
For those who might be having trouble with the picture and sound on their VIC-20, I have a solution.
It is essential that the sound and picture be adjusted properly in the RF modulator so that they are synchronized on either Channel 3 or 4. The computer is sold with the audio and video signals adjusted for one particular TV model. This may not work well on yours.
To make adjustments for your TV, carefully follow these steps:
- Turn the computer off and the TV on.
- Turn off the AFT (Automatic Fine Tuning) switch on the TV (if your set has one).
- Adjust the fine tuning knob on the TV to the middle range of that channel. Don't worry if the picture is partly fading or the sound is distorted at this point.
- Open the RF modulator very slowly and carefully. Be sure your power is off. Remove the casing screw and slowly lift the cover.
- Turn on your power for the computer.
- There are two holes which have screws in the metal casing. The one closest to the channel selector switch is the video signal. The other is for audio (see figure). Using only a small nonmetallic screwdriver, adjust the video signal until the TV picture is crisp and sharp. This acts like another fine tuning knob. Check the other channel and make sure it is in the middle of the RF signal range by adjusting the fine tuning knob on your TV.
- Adjust your TV volume to about one-half. Now adjust the audio signal level in the RF modulator until a quiet, clear sound is heard on the TV.
- Make sure that, on the other channel, both audio and video signals are perfectly adjusted.
- Turn the computer off and replace the cover on the RF modulator.
We tried your suggestions and they work very well indeed. However, we do not advocate hardware modifications except when performed by qualified, experienced technicians. Readers should be extremely careful when making internal adjustments on any electrical component. Also, tampering with the RF modulator will void your warranty. (Later versions of the VIC RF modulator may not have the adjustment screws.)
We tested this also on the internal RF modulator in the 64 but found no appreciable difference in screen or audio quality. If we hear of anything significant on this, we'll publish it in a future issue.